Re: int 0x13 utility

On Sat, 22 Mar 2008 16:27:30 -0700, I waved a wand and this message
magically appears in front of dave:

Lets start with the formula: 1024 * 256 * 63 * 512 = 8,455,716,864.
Most BIOSes do not use 1024 and 256, but subtract one from each. That
is somewhat an artifact of the old IBM AT where the last cylinder was
never allocated to allow the IBM Advanced Diagnostics to use it for
read/write testing of the old MFM hard drive.

Yes, that's correct according to the various documentation I've seen on
the 'net for the AH = 8 / Int 0x13 BIOS calls.

The extended BIOS functions INT 13h, functions 4Xh allow packets to be
used to detail larger hard drives. I do not believe that MS-DOS 6.22
will use that access method, but I know that MS-DOS 7.x does. It
shipped with Windows 95, 98, 98SE, and Me in various minor version
numbers. I believe that IBM DOS was updated to handle this access.

Thanks for reminding me about MSDOS 7.x, I'll look into that as well.

Most SATA controller vendors probably don't even think about MS-DOS
anymore. You could write a small device driver that would hook INT
13h and for the second drive return a CHS value that is larger. I
would also consider disabling any ATAPI/IDE controllers on the
motherboard so the new drive is assigned 80h for the DL value.

They ought to; there's still a lot of people using DOS these days.

I personally use USB drives to boot MS-DOS whenever I need it, but it
does require a later motherboard compared to the Pentium III.

Again that's down to the BIOS having the appropriate calls to be able
to boot off CDROMs / USB keys.

Thanks for the information.

I'm now busy on another project; a sub-2k program to scan the PCI bus
and print out all devices on it.

Regards,
Alex
--
http://www.munted.org.uk

Fearsome grindings.

.

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